Melanoma is the most deadly form of skin cancer. Although melanoma has a relatively low death rate compared with other cancers as it is generally easy to see on the skin and can be simply removed, it quickly becomes deadly if the superficial tumor metastasizes to other parts of the body. In metastasis, circulating melanoma cells (CMCs), cells that have broken off from the original tumor site and move through the blood or lymphatic system, can plant themselves elsewhere and create secondary tumors that are subsequently the cause for terminal melanoma. Accordingly, early diagnosis will likely be the cure to cancer, as the treatments have higher chances of success because the cancer has not fully manifested itself yet.
Furthermore, it is predicted that in 2010 over 68,000 Americans will be diagnosed with the disease and over 8,000 melanoma patients will die from the illness. Nevertheless, melanoma can be easily cured if it is detected early and quickly removed from the skin; however, if it metastasizes, the cancer can become lethal. Considering that a 1 mm diameter tumor typically consists of one million cells, larger more visible tumors can generally consist of billions of cells. That said, a patient who is diagnosed from a large tumor will have reduced options and will necessitate more physically demanding treatment than a patient who is diagnosed before secondary tumors can form. Unfortunately, patients must currently wait months to know if the superficial melanoma tumor has spread, because the current methods of diagnosing metastatic cancer are through imaging techniques, which require the presence of a visible metastatic tumor. Consequently, patients are oftentimes diagnosed too late.
Current methods for diagnosing metastatic cancer include lymph node biopsies and imaging techniques. However, lymph node biopsies can produce false negatives if the cancer did not interact with the lymphatic system and cannot be performed numerous times for disease monitoring. That said, circulating tumor cells can be an excellent source of information for diagnosis and monitoring of metastatic melanoma and other pathological diseases if they can be detected in the lymphatic system or blood stream. For that reason, many techniques are being investigated to detect and isolate these cells for both diagnostic and disease monitoring purposes. Some research has already been conducted to find CMCs, including RT-PCR, immunohistochemistry, magnetic cell sorting, fiber optic array scanning technology, and microfilters; however, high false negative rates, labeling, and long procedures limit chances of clinical implementation.
Unfortunately, the current methods used to diagnose metastatic disease are not sensitive to single metastatic cells. Patients must wait until secondary tumors are formed before they can be diagnosed and begin life saving treatment.